1. Field of the Invention
This invention relates to reflection print material for photographic images and more particularly to paper support for photographic light sensitive elements and the method of preparing the same.
In the preparation of paper supports for use in photographic applications and particularly color negative-positive papers, a commercial method of preparation includes the internal acid sizing of the paper utilizing compounds such as stearic acid and the like. Such papers when employed in photographic applications provide excellent resistance against aqueous solutions and do not oxidize thereby providing excellent brightness and whiteness stability of the resulting paper and photographic images developed on the paper.
For many photographic applications the paper support is coated with a hydrophobic polyolefin in order to render the paper less susceptible to the various aqueous solutions through which the paper is passed during development. The various layers, including the light-sensitive emulsion layers, are applied to the polyolefin coated paper.
The polyolefin coated paper support is converted into light sensitive print elements for use in photographic applications in manners known and commonly used in the art by the application of one or more silver halide emulsion layers and, optionally, subbing layers, interlayers such as, tie layers, overcoat layers and the like which provide desired physical and/or sensitometric properties in the photographic material.
Photographic materials, such as briefly described above, are known to exhibit changes in their sensitometric properties on storage. The passage of time, exposure to heat, and/or the exposure to high humidity conditions, can cause deterioration in the material which is evidenced as an increase of minimum density (referred to as fog) after processing to provide a viewable image. This characteristic is commonly referred to as "raw stock keeping".
It has been learned through tests that the raw stock keeping characteristics of internally acid-sized photographic papers having built thereon the necessary layers to convert the paper support into a photographic print material are very satisfactory as the minimum density of such materials does not increase substantially over storage periods. However, when the acid-sized paper is first coated with a polyolefin layer prior to building the photographic layers thereon, the raw stock keeping characteristics diminish dramatically. That is, for such structures, the minimum density increases substantially over periods of time in storage. This problem has been observed to be even more acute where the silver halide employed in the emulsion layer is silver chloride or has a high silver chloride content. With the advent of rapid processing apparatus, which includes shorter development, washing and drying cycles, higher chloride content silver halides are desirable because of their ability to be processed at increased speeds. While it is not understood why the presence of a polyolefin layer between the paper support and the remaining layers of the photographic print material would have an influence upon the raw stock keeping of acid-sized papers, it is desirable to provide an acid-sized paper support coated with a polyolefin layer which does not suffer these disadvantages.